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Disease Control and Pest Management

Modification of the Peanut Leaf Spot Advisory for Use on Genotypes with Partial Resistance. C. A. Matyac, Research associate, Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616, Present address: Department of Food Science and Microbiology, North Carolina State University; J. E. Bailey, Assistant professor, Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616. Phytopathology 78:640-644. Accepted for publication 14 December 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/Phyto-78-640.

The effects of modification of the peanut leaf spot advisory program were evaluated on six peanut genotypes in three field experiments in North Carolina in 1985 and 1986. Relative humidity-temperature index values from the Jensen and Boyle model were modified by factors of 0.85 and 0.70. The average numbers of fungicide applications were 7.0, 5.3, 4.0, and 2.6 for the 14-day schedule, standard advisory, 0.85 modified advisory, and 0.70 modified advisory treatments, respectively. Individual comparisons among all genotype-spray schedule combinations indicated that either of the advisory modifications could be used with three genotypes with leaf spot resistance, NC5, NCGP343 × NC5 (Entry 86), and NC6, without resulting in significantly greater AUDPCs, AUDEFCs, and infection rates than the nonmodified advisory. However, comparisons across all genotypes and locations indicated that the modified advisories resulted in significantly larger area under the disease progress curves (AUDPCs), area under the defoliation curves (AUDEFCs), and apparent infection rates but no significant reduction in yield. Yield loss models developed for each genotype had similar slopes indicating uniform yield responses to leaf spot among varieties.